Magnetic caliper for sheet material handling apparatus



May 5, 1953 G. F. WATSON 2,637,552

MAGNETIC CALIPER FOR SHEET MATERIAL HANDLING APPARATUS Filed April 1, 1952 6 Sheets-Sheet 1 y 5, 1953 G. F. WATSON 2,637,552

MAGNETIC CALIPER FOR SHEET MATERIAL HANDLING APPARATUS Filed April 1, 1952 6 Sheet-Sheet 2 lam n mam mi y 5, 1953 G. F. WATSON 2,637,552

MAGNETIC CALIPER FOR SHEET MATERIAL HANDLING APPARATUS Filed April l, 1952 6 Sheets-Sheet 3 G. F. WATSON May 5, 1953 \MAGNETIC CALIPER FOR SHEET MATERIAL HANDLING APPARATUS Filed April 1, 1952 6 Sheets-Sheet 4 wiuzi zaz G. F. WATSON May 5, 1953 MAGNETIC CALIPER FOR SHEET MATERIAL HANDLING APPARATUS Filed April 1, 1952 s Sheets-Sheet 5 PARAMAGNETIC y 5, i953 G. F. WATSON 2,637,552

MAGNETIC CALIPER FOR smqsg MATERIAL HANDLING APPARATUS Filed April 1952 s Sheets-Sheet s or-l.

Sparqp E Wdlsgn Patented May 5, 1953 MAGNETIC CALIPEE FOR SHEET MATERIAL HANDLING APPARATUS George F. Watson, Racine, Wis., assignor to The Christensen Machine Company, Racine, Wis., a corporation of Wisconsin Application April 1, 1952, Serial No. 279,871

28 Claims.- 1

this invention, as in the application of George 2". Watson, Serial No. 153,519, now abandoned, of which application is a continuation-in-part, relates to sheet material handling apparatus such feeders for feeding sheet of paper to printing presses and similar machines and refers particularly to a detector or caliper for stopping the apparatus upon the detection of an abnormal overlapped condition of the sheets moving to the machine being fed.

A copending application, Serial No. 153,520, filed April 3, 1959, discloses and claims the adaptation of the principle of the instant invention to caliper-mg devices or general utility.

While the use of detectors or calipers for sheet material handling apparatus is not new, those heretofore employed were either pneumatic as in Patent No. 2,063,479 issued to Frank. B. Belluche, or mechanical. The latter type, of which Patent No. 2,179,517 issued to M. Pelosi is an example, has cooperating ieele-r members, generally rollers, which have to be very accurately fitted to one another and very rigidly mounted so as to assure against any possible relative movement between their supports. This has restricted their location to the side edges of the sheet since it is impractical. if not in fact actually impossible to obtain the necessary rigidity at any substantial distance in from the side edges.

Of curse,it is to be understood that where the stock fed has substantial thickness, for instance cardboard, the presence of an abnormal sheet thickness is more easily detected. Deviations of a few thousandths of an inch in the spacing between the supports for the companion feelers is then not too serious; but where very thin paper, as for instance Bible stock, is being fed, such slight changes in the spacing between the supports of the ieeler members are fatal to accuracy.

The pneumatic or suction type calipers of Patent No. 2,663,479 while not subject to the aforesaid limitations of the mechanical calipers cannot detect an abnormal overlap or double sheet thickness where the sheets are adhered to one another and cannot be separated by the available suction.

In recognition of these limitations of the sheet detectors and calipers heretofore available, the present invention has as its purpose to provide a caliper which will not only positively detect any abnormal sheet thickness but in addition will be reliablv accurate no matter where it is located Etc-rosette width of the machine. This removes the objectionable limitation upon the location of the calipers which heretofor had to be at the side edges where thin stock wa being fed, and in addition enables the use of any desired number of calipers side by side across the width of the machine.

A novel adaptation of magnetic force makes these advantages possible. As will appear more fully hereinafter, the present invention so utilizes the force of a permanent magnet that the companion ieeler member between which the paper travels, themselves may constitute the elements of a magnet couple. In any event, the elements of the magnet couple are fixed with respect to the feeler members so that the elements of the magnet couple are moved simultaneously and directly with any movement of the feeler members. Thus, the magnetic attraction between the magnet couple directly holdsthe sheet engaging surfaces of the feeler members against the opposite sides of the sheet in opposition to a biasing force tending to separate the feeler members and operable, upon being released, to actuate instrumentalities {or stopping the apparatus.

This novel adaptation of magnetic force enables the elements of the magnet couple to be so disposed with respect to one another that the strength of the magnetic attraction therebetween depends solely upon the spacing between the ieeler members.

This invention provides, therefore, what may be termed a magnetic caliper especially adapted fo use on paper sheet feeders and inspection machines, through which the slight motion obtained by relative movement between companion feeler member resulting from the detection of an abnormal overlapped condition of the sheets traveling along a defined path and passing between the companion feeler members is translated into a greatly magnified motion which takes place with a snap action and possesses considerable force.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of part substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiments or". the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrate several complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Fi ure l is a side elevational view of a sheet feeder etluipped with the calipering device of this in ention Figure 2 is a cross sectional View through the calipering device on a larger scale illustrating the same in its operative condition;

Figure 3 is a view similar to Figure 2 but showing the calipering mechanism tripped;

Figure 4 is a top plan view of the calipering mechanism with parts thereof broken away and in section;

Figures 5 and 6 are cross sectional views similar to Figures 2 and 3 but illustrating the incorporation of an inhibiting or lock-out device for the caliper;

Figure '7 is a top plan view of the structure shown in Figures 5 and 6;

Figure 8 is a front view of another adaptation of this invention, parts thereof being broken away and in section, said view illustrating one way of arranging a plurality of magnetic calipers across the width of the machine and a simplified manner of simultaneously adjusting all of the calipers to difierent thicknesses of stock;

Figure 9 is a front view of one form of the magnetic caliper of this invention illustrating how a horseshoe magnet may be substituted for the annular magnets used in those embodiments of the invention illustrated in Figures 1 to 8, inelusive;

Figure 10 is an end view of a magnetic caliper, which like the one shown in Figure 9, uses a horseshoe magnet;

Figure 11 is a front view of the caliper shown in Figure 10;

Figure 12 is a top view of the lower element of the magnetic caliper shown in Figure is, said view being taken on the plane of the line l2l2 in Figure 10;

Figure 13 is an end view of a magnetic caliper or detector embodying still another modification of this invention;

Figure 14 is a diagrammatic top View of two adjacent rows of magnetic detectors of the type shown in Figure 8 arranged to encompass the full width of the passing sheets and thereby reliably inspect all portions of the sheets as they pass; and

Figure 15 is a cross sectional view through the two rows of detectors illustrating oneway of mounting the movable elements thereof for independent action.

Referring now particularly to the accompanying drawings, and more specifically to the embodiment of the invention shown in Figures 1 to 4, inclusive the numeral 5 designates generally a sheet feeder, which, as shown, may be of the continuous type wherein the supply of sheets to be fed is loaded onto the feeder in a fanned out bank. As is customary, the feeder includes separating mechanism 6 adapted to successively separate the sheets from the bank and feed them to a suitable conveying means 1 by which the sheets are carried or advanced in seriated or under-lapped relation to the press 8 or other machine being red. The conveying means 1 includes the customary feed board 9 over which the sheets are fed in their final passage to the press and upon which the sheets are front and side registered just before entering the press, it being understood that the sheets enter the press one at a time.

Although the sheets are carried along or advanced by the conveying means in a seriated stream, the presence of two or more sheets adhered to one another or any other abnormal overlapped condition of the sheets can be detected by the thickness of the stream of sheets moving to the press. Obviously, if the thickness of the stream exceeds a predetermined maximum, it is an indication that an abnormal overlapped condition exists and that the feeder should be stopped. This is the function of the calipering device indicated generally by the numeral I0.

Essentially, the calipering device I t comprises a pair of companion feeler rollers l I and i2 between which passes the stream of sheets S. The roller !2 which is power driven is located beneath the path of the stream of sheets 8 and rotates on a fixed axis. The roller H, which is located above the path of the sheets, is carried by an arm l3 which is pivoted as at l3 upon a supporting bracket M. The supporting bracket i4 is mounted upon a transverse shaft l5 fixed to the side frames l5 of the feeder, a portion of only one of which is shown. To enable the position of the calipering device to be adjusted to sheets of different widths within the range of the feeder, the bracket [4 is slidable along its supporting shaft [5 and may be locked in any position thereon. It is, of course, evident that if desired any number of calipering devices may be arranged side by side upon the shaft !5 in which case the lower rollers [2 of all of the calipers are mounted upon a common drive shaft.

Swinging of the lever arm 53 about its pivot i3 raises and lowers the roller II as will be readily apparent, and as a correlary, up and down movement of the roller H from and toward its companion roller 52 occasioned by variations in the thickness of the stream of sheets S passing between the rollers, imparts corresponding rocking motion to the lever arm l3.

Separation of the feeler rollers II and I2 is opposed by magnetic attraction therebetween. To this end a permanent magnet I6 is built into the roller l l and the roller I2 is formed of paramagnetic material or at least is essentially of paramagnetic material. The magnet I6 is annular so that the axial ends or opposite sides thereof are of opposite polarity, and to provide poles for the magnet the roller I I is made up of two complementary facing cup-shaped halves ll of magnetically permeable material which together house the magnet but have their edges spaced apart. While the space between the edges of the roller sections I! could be left open, to preclude the accumulation of dirt therein and the possible bridging of the magnet poles by iron filings and the like, it is preferably filled with a suitable non-magnetic sealing compound l8.

The roller II is free to revolve about its axle [9 which is secured in the lever arm I 3 so as to ride freely upon the driven roller l2, if the two are in engagement, or upon the sheets passing therebetween; and by virtue of the attraction between the permanent magnet l6 and the lower roller l2 which two members constitute the elements of a magnet couple, the rollers H and I2 firmly clamp the sheets therebetween. Hence, the space betweeen the peripheries of the rollers is a true measure of the thickness of the sheets passing therebetween.

The magnetic attraction which draws the rollers l l and I2 together is opposed by a spring 20, confined between a fixed stop 2| on the bracket l4 and an adjustable stop 22 in the form of a nut threaded upon a stem 23 pivoted, as at 24, to the lever arm [3 and slidably guided in the mentalities.

stop 2!. By means of the adjustable stop 22, the tension of the spring may be so adjusted that the force of the spring is overbalanced by the magnetic attraction drawing the feeler rollers H and i2 together as long as the space, between the peripheries of the rollers does not exceed a predetermined critical distance. When this happens the spring is freed and produces a snap action motion of considerable force. The adjustable spring stop thus provides the means by which the detector may be adjusted to stock or sheets-of different thicknesses.

The spring produced motion is utilized to rock .a control actuating shaft 25, and through such rocking motion thereof, actuates the control instrumentalities not shown) by which the feeder may be stopped. Linkage 26, shown in Figure 7, connects the shaft with the control instru- To enable the spring produced motion to impart such rocking movement to the shaft 25, a lever 2'! is slidably splined to the shaft and carries a pin 23 at its outer end to provide an abutment against which the adjacent end of the stem 23 bears. With this arrangement, the

very slight motion resulting from the movement of the roller I l away from its companion roller 12 produced by the interpcsitioning of one additional sheet between the rollers is translated into a greatly magnified motion which takes place with a snap action and possesses considerable force.

This follows from the fact that as long as the elements of the magnet couple are relatively close together, as they are in this case, being separated only by the thickness of the stream of sheets, the magnetic attraction therebetween is quite strong especially if light paper sheets are being handled. In practice the magnetic pull would be on the order of twelve pounds where the distance between the feeler rollers is .004, seven pounds for twice this spacing and four pounds for three times this thickness. Hence, the reacting spring has a strong force stored therein so that whenever the spacing between the elements of the magnet couple reaches the critical distance at which the spring force overpowers magnetic attraction, a relatively powerful force is released with a snap.

In the stream feeding of sheets, the trailing portion of each sheet always overlaps the leading portion or" the next adjacent sheet. Hence, the spring tension of the caliper must be adjusted to accommodate twice the thickness of a single sheet, but the addition of a third sheet thickness should trip the caliper as shown in Figure 3.

In the stream feeding of long sheets, the trailing portion of each sheet may overlap the leading portion of the sheet following the next adjacent one as shown in tires 5 6. To permit; such overlapping and still have the caliper set to tripin response to a third sheet thickness, an inhibitor or lock-out device is provided in that form of the invention shown in Figures 5, 6 and 7. This inhibitor or lock-cut device consists of an arm 38 keyed to a cross shaft 3% parallel to and in front of the supporting shaft E5. The shaft 3i is freely rotatable in a bearing carried by bracket i l and has one end thereof projecting through one of the side frames of the feeder to mount driving linkage 32. This driving linkage rocks the shaft ill to bring the arm it against the adjacent por tion of the lever ill just before the triple overlap to be permitted reaches the feeler rollers ll and i2, and holds it there until this overlap passes the rollers.

To permit the slight separation of the rollers necessary to pass the triple overlap, the linkage 32 is spring propelled in the direction to bring the arm 30 into operative position shown in Figure 6 and cam actuated to retract the arm as in Figure 5.

As indicated hereinbefore, the calipering rollers may be located at any point across the width of the machine, and any number of sets or pairs of calipering rollers may be employed alongside each other to provide a row of detection points extending transversely across the path of the sheets. Where such multiple points of detec tion are desired, it may be preferable to embody the invention in the form illustrated in Figure 8. In this case, all of the lower rollers 38 are mounted on a common driven. shaft 23 i ournallecl in sleeves 35 carried by the side frames 36 of the feeder or other machine with which the device is used. Since in this case the magnet is in the lower one of the pair of rollers, each roller 33 is constructed in the manner shown in Figure l, that is, each comprises a pair of opposed cupshaped members ll enclosing the annular magnot it but spaced apart at their peripheries by a non-magnetic spacer l8.

Non-magnetic spacers 3'! are interposed between the rollers 33 and the entire assembly is clamped together to form one solid roller unit. The ends of this roller unit or assembly abut the bearing sleeves which, being threaded in their respective side frames 36, may be shifted axially. This arrangement provides a convenient manner of simultaneously and quickly shifting all of the rollers 33 axially one way or the other, and to secure the same in selected. adjusted positions lock nuts 33' are provided.

As will appear more fully hereinafter the axial or endwise adjustability of the lower roller unit affords a convenient and simple manner of simultaneously adjusting all of the detector or caliper units to work with different thicknesses of stock.

Since the lower rollers 33 in this case contain the magnet, the companion upper rollers 38 are of paramagnetic material. Each roller 38 is carried in a yoke 32? which is pivotally mounted as is the bracket 53 in Figure 2 so that each roller 38 is individually movable toward and from its companion.

A suitable spring arrangement diagrammatically indicated as at fill and which may be like that illustrated in Figure 2, yieldingly urges each roller 38 upwardl and away from its companion roller 33 without affecting any of the other calipers. Thus, the passage of an abnormal overlapped sheet condition between the companion rollers of any one caliper or detector unit can be utilized to stop the mechanism in the manner hereinbefore described.

In first setting up the caliper illustrated in Figure 8 each spring ll} must be individually adjusted to the desired sheet thickness so that all of the detector units will respond to the same critical separation between rollers. Thereafter whenever it is desired to change the adjustment to accommodate different sheet thicknesses, it is only necessary to shift the lower roller a bly one way or the other to thereby bi the lower rollers 33 further into or further out of symmetr with their companion upper rollers 38. The full line position of the parts shown in Figure 8 illustrates the rollers in complete symmetry which, of course, aliords the stron t magnetic attraction between the rollers since in this position the reluctance of the magnetic circuit is least, whereas in the dotted line position 7. of the lower roller assembly the magnetic attraction between the rollers is greatly diminished because of the assymmetrical disposition of the rollers of each pair and the consequent increase in reluctance in the magnetic circuit.

Obviously, of course, the magnet could be mounted in the upper roll as it is in the previously described embodiments of the invention. In this case the lower roll assembly would consist of a series of collars of paramagnetic material separated by non-magnetic spacers. Either arrangement lends itself admirably to the adaptation of this invention to the inspection of sheet material or separate sheets where it is esesntial that the entire area thereof be calipered. Such an adaptation of the invention is diagrammath cally illustrated in Figure 14 where sheets S move successively along a defined path between two rows of detector units R and R.

Each of the two rows of detector units consists of a continuous lower roller assembly 45 and a series of independent upper rollers 52. The lower roller assembly til may contain the magnets as in the structure shown in Figure 8, and as there indicated is mounted for axial adjustment in the manner described in connection with Figure 8.

The upper rollers 42 thus are independently mounted for movement toward and from their companion bottom rollers, and it is important to observe that the relative spacing of these upper rollers with respect to their widths is such that the upper rollers of one row ride upon the surface of the sheets lying between the upper rollers of the other row. In other words, the upper rollers of the two rows are staggered to assure that the entire area of the sheets will be caliper-ed.

Though the manner in which the upper rollers 42 are mounted may be varied to suit different conditions and may follow the arrangement shown in Figure 2 for instance, a convenient and compact arrangement for the mounting of these upper rollers is illustrated in Figure 15. As here shown each roller 42 is carried by a lever-like bracket 43 pivoted as at 44 upon a crosshead 45. All of the crossheads 45 are slidably mounted upon two parallel transverse supporting rods 46 so that the upper rollers 42 can be axially adjusted with respect to each other as needed to effect the desired staggered relationship and assure the entire area of the sheets being calipered.

Each lever-like bracket 43 is individually yieldingly urged by a spring 4'! to lift its roller 42 and, as hereinbefore described, such spring propelled movement of the movable roller takes place whenever the thickness of the sheets passing between the calipering rollers exceeds the predetermined critical value.

Upon sprint: produced movement of any one of the lever-like brackets 63 one or the other of two actuating shafts 48 is rocked. To this end the brackets 43 are each individually connected with one of the shafts 58 through a link 49 and a lever 50, the latter keyed to the shaft 43. Lost motion is provided in the connections between the links and levers as shown to allow the actuated bracket 43 to rock its shaft without hindrance from the rest of the mechanism.

The rocking of either one of the shafts 48 may be utilized in any suitable manner either to stop the passage of sheets upon detection of an abnormal overlapped condition or to control mechanism (not shown) by which an imperfect sheet will be discarded, but since the specific vway in which such response is utilized to effectuate the desired result forms no part of this invention, it is sufficient to diagrammatically illustrate the same as has been done in Figure 15 wherein a switch 5| connected with each of the two shafts 48 closes a circuit controlling the mechanism to be actuated, whenever either shaft is rocked.

In all of the embodiments of the invention described thus far the magnet has been annular and actually embedded in one of the two cooperating rollers. It is, of course, also possible to utilize the more conventional horseshoe magnet without deviating from the spirit or scope of this invention and those modifications of the invention shown in Figures 9 to 13, inclusive, use this more conventional form of magnet.

Thus, in Figure 9 the upper roller 52 is formed of any suitable non-magnetic material and is mounted in a yoke 53 to which a horseshoe magnet 54 is securely fastened. The ends or poles of this horseshoe magnet lie in a plane spaced slightly above the horizontal plane tangent to the underside of the roller 52 so as to be spaced slightly from the adjacent surface of the lower roller 55 which coacts with the roller 52 and is formed of paramagnetic material. The magnet couple in this case, of course, constitutes the lower roller 35 and the horseshoe magnet 54, but since the horseshoe magnet 54 is fixed with respect to the axis of the upper roller 52 it follows that the strength of the magnetic attraction between the elements of the magnet couple depends solely upon the spacing between the rollers.

In the embodiment of the invention illustrated in Figures 10, 11 and 12, the horseshoe magnet 56 is disposed horizontally with its legs embracing the sides of the lower roller 57 which, in this case, is of non-magnetic material carried by a drive shaft 58 journalled in a bearing bracket 59. The bearing bracket 58 also has the horseshoe magnet secured thereto so that the magnet will be fixed with respect to the axis of the roller 51; and though any suitable manner of mounting the bracket 59 may be employed it is convenient to secure the same to a transverse supporting rod 60 by means of a set screw so that the position of the bracket 59 may be adjusted across the width of the machine.

In this embodiment of the invention the upper roller (ii is of paramagnetic material and is carried by a bracket 62 to move up and down as in Figure 2.

The embodiment of the invention illustrated in Figure 13 differs from those previously discussed in that neither one of the rollers need be of paramagnetic material. Accordingly a horseshoe magnet 63 embraces the lower roller 54 and is held in fixed relation to the axis thereof by having the bearing bracket 65 in which the roller is journalled fixed to the bight of the horseshoe magnet. The poles of the magnet are secured to the underside of a horizontal supporting plate 66 of non-magnetic material which in turn is mounted upon a transverse supporting shaft 61.

The upper roller 58, which as indicated may be of non-magnetic material, is carried by a. supporting bracket pivotally mounted upon a ross shaft 753. A spring H yieldingly urges the roller 58 away from its companion, but the spring is resisted by the magnetic attraction between the horseshoe magnet and an armature 12 of paramagnetic material. The armature 12 is fixed with respect to the axis of the upper roller 68, being mounted upon the axle of the roller as accuse shown, and an adjusting screw13 reacting against a spring '14 enables the armature to be brought into absolute parallelism with the supporting plate 63 and consequently the pole faces of the horseshoe magnet.

The operation of this embodiment of the invention is, of course, the same as that hereinbeiore described since, as in all previous in stances, the separation of the rollers beyond a predetermined critical distance enables the spring to overpower the magnetic attraction and thus impart a snap action movement to the movable element of the detector unit.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that the present invention provides a calipering device for sheet feeders, sheet inspecting machines, and sheet material handling machines generally which is simple in construction and positive in its operation, and which is not limited in its application to the side edges of 'the sheets but may be located at any position across the width of the machine with assurance of absolute accuracy and without the need for heavy supporting structures. This follows from the fact that any deviation of the stationary one (described and shown as the bottom one) of the pair of feeler rollers caused by flexure or vibration of its supporting shaft or by any other cause which might be encountered in machines of this type, in nowise afiects the functioning or positiveness of the caliper since in this case the other roller of the'pair (the upper one) merely rises and falls with the stationary roller without tripping the mechanism as long as the spacing between the rollers does not exceed the critical distance for which the mechanism has been set by the adjustment of its spring tension.

What I claim as my invention is:

1. In a sheet material handling machine including conveyor means by which the sheet ma-- terial is carried along a defined path, means for effecting a predetermined response of control instrumentalities for said machine upon passage along said defined pathofan abnormal condition in the thickness of the sheet material, comprismg: a pair of cooperating rollers positioned to engage the opposite faces of sheet material moving along said defined path So that such sheet material must pass between the rollers; means mounting one of said rollers for movement to of one of the rollers and positioned to be directly I adjacent to one face of the sheet material being carried along by the conveyor means, a magnet firmly fixed with respect to the axis of said other roller and positioned to lie directly adjacent to the other face of the sheet material passing between the cooperating rollers, the poles of said magnet being in juxtaposition to said body of paramagnetic material so that the strength of the magnetic attraction between the magnet and said body of paramagnetic material depends solely upon the spacing between the rollers; biasingmeans acting upon the movable roller and yieldingly urging the same away from the other, said biasing means being overpowered by magnetic attraction between the 10 distance; and means actuated by the separation of the rollers by the biasing means and operable in consequence to such actuation to effect the dc sired response of the control instrumentalities.

2; In a sheet material handling machine: a pair of cooperating feeler members between which thesheet material passes with its opposite faces in direct! contact therewith. so that the thickness of thesheet. material determines the spacing between the feeler members; one of said feeler members being movable toward and from the other; amenable-control member forming part of control instrumentalities forv the machine; a connection between the movable control member and the movable ieeler member through which an appreciable movement of the feeler member away from. its companion actuates the control member; a body of paramagnetic material fixed with respect to one of the feeler members and positioned to be directly adjacent to one face of the sheet material passing between said co operating feeler members; a magnet firmly fixed with respect to the other feeler member and positioned at. the. other. face ofv the sheet material passing between the feeler members, with the poles of the magnet in juxtaposition to said body of paramagnetic material. so that the strength of the magnetic attraction between the magnet and said body of paramagnetic material depends solely upon theispaci'ng between the 00- operating feeler members; and biasing means yieldingly urging the movable feeler member away from its companion and thereby tending at all times to actuate the control member, said biasing means being overpowered by the magnetic attraction between the magnet and said body of paramagnetic material as. long as the feeler members are spaced apart less than a predetermined distance so that separation of the feeler members in excess of said distance as by the interpositioning of an abnormal condition in the thickness of the sheet material passing between the feeler members overpowers the force of magnetic attraction;

8. In a sheet ca-lipering mechanism for a sheet material handling. machine; a pair of cooperating feeler members between which the sheet material passes, one of said members being'movable-toward and from the other; a movable control member formin part of control instrumentalities for the machine; an operable connection between the movable control member and the movable feeler member through which a substantial movement of; the f-eeler member away from its: companion actuates the control member; biasing means'yield-ingly urging the movable feeler member away from its companion and thereby tending at all. times to so actuate the control member; apermanent magnet mounted in one of said feeler members and having its poles facing the other feeler member; and said other feeler member being essentially of paramagnetic material so that the feeler members are magnetically drawn together in opposition to said biasing means and the biasing means is restrained. as long as the feel e'r members are spaced apart lessthan apredetermined distance, separation of the feeler members-in excess of said distance, as by the'interpo'sitioning of an abnormal condition in the thickness ofthe sheet material passing between the feel'er members, en'- abling th'ebiasing means to overpower the force of m-ag'neticattraction drawing the feeler members together.

4:111 aisheet feeder having separator mech- I 1. ahism for successively separatin sheets from a source thereof and conveyor means for advancing such separated sheets in seriated relation along a defined path to a machine to be fed, means for stopping the feeder upon the detection of an abnormal overlapped condition of the stream of sheets moving along said conveyor means, comprising: companion feeler rollers positioned to engage the opposite faces of the stream of sheets being advanced by the conveyor means so that the stream of sheets passes between the rollers; means mounting one of said rollers for rotation about a fixed axis; a pivoted support for the other roller by which said other roller is movable toward and from the first roller; a movable control member operable to effect stopping of the feeder; a connection between the movable control member and said pivoted support through which movement of the pivoted support in the direction to separate the rollers actuates the control member; biasing means urging said pivoted support in said direction and thus tending at all times to separate the rollers; a permanent magnet within one of said rollers; and the other roller being of paramagnetic material so that the two feeler rollers constitute a magnet couple and the magnetic attraction therebetween draws the rollers together in opposition to said biasing means, said biasing means being overpowered by the magnetic attraction between the elements of the magnet couple as long as the spacing between the rollers which is determined by the thickness of the stream of sheets passing therebetween is less than a predetermined critical distance.

5. The apparatus set forth in claim 4 further characterized by the provision of means operating in timed relation with the feeder restraining the biasing means notwithstanding its release by separation of the rollers the critical distance so that a regularly recurring overlopped condition of the sheets does not trip the mechanism.

6. In a sheet feeder for feeding sheets from a source of supply to a printing press or other machine to be fed and including a conveyor for carrying the sheets along a defined path to the machine being fed, means for detecting the passage along said defined path of an abnormal condition in the thickness of the sheets and for actuating a control member, comprising: companion feeler members each having a sheet engaging surface; means mounting and positioning said feeler members with their sheet engaging surfaces facing each other and in position to engage the opposite faces of sheets moving along said defined path so that the sheets pass therebetween, the mounting means for one of said feeler members providing for movement thereof toward and from its companion; a magnet embodied in one of the feeler members, and the other feeler member having a paramagnetic portion defining its sheet en aging surface so that said feeler members are drawn together by the magnetic attraction therebetween; biasing means acting upon the movable feeler member and yieldingly urging the same away from its companion, said biasing means being overpowered by the magnetic attraction between the feeler members as long as the spacing between their sheet engaging surfaces does not exceed a predetermined critical distance but separating the feeler members whenever the spacing between said surfaces exceeds the critical distance; and a movable control member actuated by the biasing means upon release of the biasing means.

7. In a sheet material handlingmachine hav- 12 mg control instrumentalities to be actuated upon the detection of an abnormal sheet thickness: conveyor means for advancing the sheet material along a defined path; a pair of cooperating feeler members; means mounting and positioning the feeler members with their sheet engaging surfaces facing each other and in position to engage the opposite faces of the sheet material advancing along said defined path; the mounting means for one of said feeler members providing movement of said member toward and from the other; a movable actuating member for the control instrumentalities; an operable connection between the movable actuating member and the movable feeler member through which movement of said feeler member beyond a predetermined distance away from its companion operates said actuating member to actuate the control instrumentalities; biasing means yieldingiy urging the movable feeler member away from its companion and thereby tending at all times to so operate the actuating member; a permanent magnet consti tuting part of one of the feeler members, and said feeler member having spaced magnetically permeable portions providing poles for the magnet and also the sheet engaging surface of said feeler member; and the other feeler member being essentially of paramagnetic material and bridging said poles of the magnet so that the feeler members are drawn toward each other by magnetic attraction, whereby said movable feeler member is restrained by said magnetic attraction against being moved by the biasing means as long as the feeler members are spaced apart less than said predetermined distance.

8. In a sheet material handling machine for advancing sheet material along a defined path and having control instrumentalities to be activated upon the detection of an abnormal condition in the thickness of the sheet material being advanced along said path, a magnetic caliper for detecting such an abnormal condition and thereupon activating the control instrumentalities, said magnetic caliper comprising: a pair of companion rollers having their axes parallel; means mounting one of the rollers with its axis disposed crosswise of the path of the sheet material and its periphery in position to engage one face of the sheet material advancing along said path; means mounting the other roller with its periphery in position to engage the opposite face of said sheet material and for movement toward and from its companion; one of said rollers comprising a permanent magnet between axially spaced portions of magnetically permeable material which form poles for the magnet; the other roller being essentially of paramagnetic material so as to magnetically bridge said poles whereby the two rollers are drawn together by magnetic attraction; a spring acting upon the mounting for the movable roller and tending at all times to separate the rollers, said spring being overpowered by the magnetic attraction between the rollers as long as the space between them does not exceed a predetermined critical distance; and an actuating member for the control instrumentalities drivingly connected with the mounting for the movable roller and operable by spring produced movement thereof.

9. In a sheet feeder having conveyor means for feeding sheets from a source of supply to a discharge point and instrumentalities to be actuated upon the detection of an abnormal condition in the thickness of the sheets being fed, means for detecting such an abnormal condition, comprising: companion feeler rollers; means mounting the feeler rollers in position to engage the opposite faces of the sheets being fed and for relative movement toward and from one another; one of said rollers comprising a pair of complementary disc-like sections of magnetically permeable material spaced apart a slight distance at their rims; a permanent magnet confined between saio. ions and so disposed that said sections poles for the magnet; the other roller bemg or paramagnetic material so as to magnetically bridge said poles and be attracted. towar s its companion; biasing means acting in cp ion to said magnetic attraction and operable to separate the feeler rollers when the spacin therebetween exceeds the critical distance at which the magnetic attraction overpowers the biasing means; a control element for operating the instrumentalities governed by the detector; and a driving connection which operates in accordance with separation of the feelor rollers by the biasing means to impart movement to the control element.

10. A machine for inspecting sheet material and detecting an abnormal condition in the thickness thereof, comprising: conveyor means for advancing the sheet material along a defined path; a plurality of pairs of companion feeler rollers; means mounting said pairs of companion ieeler rollers side by side in a row extending transversely across the path of the sheet material with one roller of each pair positioned to have its periphery engage one face of the advancing sheet material and the other roller positioned to have its periphery engage the opposite taco thereof, the mounting means for one roller of each pair providing for movement thereof independently of all other rollers toward and from its comp nion; separate means biasing the movable roll of each pair away from. its companion; a permanent magnet for one roller of each pair arranged with the poles thereof fixed with respect to the axis of its roller and in juxtaposition to the companion roller of the pair, the companion roller being essentially of paramagnetic material so that the rollers are magnetically attracted to one another in opposition to the force of the biasing means tending to separate them, the strength of the magnetic attraction between the rollers depending upon the distance between the rollers so that upon separation of the rollers beyond a critical distance at which the force of the biasing means overpowers the magnetic attraction, as by the interpositioning of an abnormal condition in the thickness of the sheet material passing between the rollers, the biasing means moves the movable roller away from its companion; a movable actuating member; a motion transmitting connection between the mount ing means for the movable roller of each pair of rollers and said actuating member through which motion of any one of the movable rollers produced by the biasing means operates the actuating member; and control instrumentalities connected with the actuating member to be activated thereby.

11. The machine set forth in claim further characterized by the fact that the pairs of companion feel-er rollers are axially spaced apart; and further characterized by the provision of a second actuating member and a second row oi similar companion feeler rollers disposed in staggered relationship with the companion feeler rollers of the first row with the fields of coverage of the rollers in one row overlappingthose of the other row; and further characterized by the fact that said control instrumentalitiesare responv sive to operation of the actuating member of either row of feeler rollers.

12. In a sheet material handling machine of the character described: conveyor means for advanclng sheet material along a defined path; a plurality of pairs of companion feeler rollers; means mounting said pairs of companion feeler rollers side by side in a row extending transversely across the path of the sheet material with one roller of each pair positioned to have its periphery engage one face of the advancing sheet material and the other roller in position to have its periphery engage the opposite face thereof{ the mounting means for one roller of each pair providing for movement thereof toward and from its companion; separate means biasing the movable roller of each pair away from its companion; a permanent magnet for one roller of each pair arranged with the poles thereof fixed with respect to the axis of its roller and in juxtaposition to the companion roller, said companion roller being essentially of paramagnetic material so that the rollers of each pair are magnetically attracted toward one another in opposition to the force of the biasing means tending to separate them, the strength of the magnetic attraction between the rollers of each pair depending upon the distance between them and their relative axial dispositions so that upon separation of the rollers of any pair beyond a critical distance at, which the biasing means overpowers the magnetic attraction, as by the interpositioning of an abnormal condition in the thickness of the sheet material passing between them, the biasing means acting on the movable roller of that pair moves it away from its companion; control instrumentalities operated by the motion of any one of the movable rollers produced by the biasing means; and means for simultaneously shifting all of the rollers at one side of the defined path of travel of the sheet material as a unit axially with respect to the rollers at the other side thereof to thereby simultaneously change the effectiveness with which the magnetic attraction between the rollers opposes the springs.

13. In a magnetic caliper of the character described: a pair or" companion ieeler rollers means mounting one of said rollers for movement toward and from the, other; means for passing sheet material to be calipered between said rollers; biasing means acting upon the movably mounted roller tending to move it away from its companion; a permanent magnet fixed with respect to the axis of one of the rollers with its poles facing the other roller and in juxtaposition thereto, said other roller being essentially of paramagnetic material so that the rollers are magnetically drawn together in opposition to the biasing means tending to separate them, the strength of the magnetic attraction depending upon the thickness of the sheet material between the rollers and the relative axial disposition of the rollers so that upon the interpositioning of an. abnormal condition in the thickness of sheet material, passing between the rollers the biasing means overpowers the magnetic attraction and separates the rollers; and means for shifting one of the rollers axially with respect to the other roller to thereby change the strength of the magnetic attraction drawing the rollers together.

14. In a magnetic caliper of the character described: a unitary roller assembly comprising a series of magnet rollers and non-magnetic spacers arranged alternately upon a common shaft;

a movable companion roller'for each of said magnet rollers, said movable companion rollers being essentially of paramagnetic material; a separate mounting for each of said movable rollers by which it may be moved toward and from its magnet roller; separate biasing means acting upon the mounting means of each of said movable rollers and tendin to separate it from its companion magnet roller; and means for shifting the roller assembly axiall with respect to the movable companion rollers to thereby simultaneously alter the reluctance of the magnetic circuit of each pair of rollers whereby the critical distance of separation between the rollers at which the biasing means overpower magnetic attraction may be simultaneously adjusted for all pairs of rollers.

'15. In a sheet handling machine including conveyor means by which the sheet material is carried along a defined path, means for effecting a predetermined response of control instrumentalities for said machine upon passage along said defined path of an abnormal condition in the thickness of the sheet material, comprising: a pair of cooperating rollers positioned with their axes transverse to the path of the sheet material and their peripheries engageable with the opposite faces of sheet material moving along said path so that such sheet material must pass between the rollers; means mounting one of said rollers for movement toward and from the other; a bcdy of paramagnetic material fixed with respect to the axis of one of the rollers and positioned to be directly adjacent to one face of the sheet material being carried along by the conveyor means; a horseshoe magnet embracing the other roller and fixed with respect to the axis thereof with its poles positioned to lie directly adjacent to the other face of the sheet material passing between the cooperating rollers and in juxtaposition to said body of paramagnetic material so that said rollers are drawn together by the magnetic attraction between the magnet and the body of paramagnetic material with a force depending solely upon the spacing between the rollers; biasing means acting upon the movable roller and yieldingl urging the same away from the other, said biasing means being overpowered by the magnetic attraction between the horseshoe magnet and said body of paramagnetic material as long as the spacing between the rollers does not exceed a predetermined critical distance but moving the rollers apart the instant the spacing therebetween exceeds said predetermined critical distance; and means actuated by the separation of the rollers produced by the biasing means and operable in consequence to such actuation to effect the desired response of the control instrumentalities.

16. lfhe structure set forth in claim 15 wherein said body of paramagnetic material is in the form of a bar separate frcm its associated roller but mounted upon the axle thereof with the outer face of the bar lying in a plane radially inward of the periphery of the roller; wherein the horseshoe magnet embraces the other roller with its poles opposite the end porticns of said bar of paramagnetic material; and means for adjusting said bar of paramagnetic material about the axle of its roller to enable the maintenance of uniform spacing between the poles of the horseshoe magnet and the end portions cf said bar.

17. In a magnetic caliper: a magnet couple consisting of a magnet element and an armature element mutually attracted toward one another, one of said elements being movable toward and from the other; a spring applying a force upon the movable element in a direction tending to separate the elements of the magnet couple; said elements of the magnet couple having feeler surfaces drawn toward each other by the magnetic attraction between said elements and between which work to be calipered may be passed, said elements engaging opposite faces of said work and being held by magnetic attraction against spring propelled separation beyond the thickness of said Work as long as the spacing between their said feeler surfaces remains less than a critical distance at which the magnetic attraction between the elements overpowers the spring so that the interpositioning of work having a thickness at least as great as said critical distance for which the caliper is set will cause said spring to overcome said magnetic attraction permitting said movable element to be moved out of engagement with the work by the spring.

18. A caliper of the character described, comprising: a magnet couple consisting of a magnet element and an armature element mutually attracted toward each other; one of said elements being movable toward and from the other; an indicator responsive to movement of the movable element away from the other element; feeler surfaces on said elements between which work to be calipered is passed, said feeler surfaces being engaged with opposite faces of said work by the magnetic attraction of said elements; and a spring acting upon the movable element in opposition to the magnetic attraction between said elements to move the same and actuate the indicator whenever the elements of the magnet couple are separated beyond a predetermined distance by work having a thickness greater than said pro-determined distance.

19. In a caliper of the character described: a permanent magnet having a work engaging surface; a member of magnetic material, means mounting the permanent magnet for movement in a defined path toward and from a work engaging reference surface on said member, said surfaces engaging opposite faces of work to be calipered; a spring applying a unidirectional force upon the permanent magnet, said spring being overpowered by the magnet as long as the permanent magnet is less than a predetermined critical distance from the reference surface, but overpowering the magnet and moving the same out of engagement with the work whenever the space between the work engaging surface of the magnet and the Work engaging reference surface exceeds said predetermined critical distance; indicator means responsive to spring propelled movement of the permanent magnet, whereby said indicator means is activated whenever the thickness of a layer of non-magnetic material between the work engaging surface of the permanent magnet and the work engaging reference surface separates the same more than the critical distance for which the caliper is set; and means for adjusting the tension of the spring to set the caliper.

20. In a magnetic caliper of the character described: a magnet couple comprising a permanent magnet having a work engaging surface and a block of magnetic material having a complementary work engaging surface; means mounting said elements of the magnet couple in opposed relation with their, work engaging surfaces facing each other so that the magnetic attraction between the magnet and the block tends to draw their work engaging surfaces together, one of said elements being movable toward and from the other; biasing means acting upon said movable element and at all times urging the same away from the other element to thus separate their work engaging surfaces; and instrumentalities actuated by movement of the movable element produced by the biasing means so that whenever work to be calipered is passed between said elements With opposite faces of the work engaged by the work engaging surfaces of said elements of the magnet couple which reduces their mutual magnetic attracticn by increasing the spacing therebetween to the point where the biasing means overpowers the magnetic attraction, said instrumentalities will be actuated in response to movement of said movable element by said biasing means.

21. In a magnetic caliper for non-magnetic material, a magnet couple comprising a magnetized element and an armature element magnetically attracted toward one another, said ele ments having feeler surfaces engaging directly opposed faces of the material being calipered, said engagement being efiected by the magnetic attraction of said elements, and one of said ele ments being movable toward and away from the other, support means for said elements, biasing means operably connected with and contin ously applying a yieldable force upon the movable element, said force being applied in a direction tending to further separate said elements and to disengage said movable element from said material, the biasing force and the force of magnetic attraction being so proportioned that the movable element is held in engagement with the surface of said material as long as the thickness of the material interposed between said feeler surfaces in less than a critical distance at which the biasing force overpowers the force of magnetic attraction between the elements and said movable element is moved out of engagement with the material when material having a thickness at least as great as said critical distance is v interposed between said feeler surfaces.

22. Apparatus as defined in claim 21 wherein the magnetized element is movable and the armature element is fixed.

23. Apparatus as defined in claim 21 wherein the armature element is movable and the magnetized element is fixed.

24. Apparatus as defined in claim 21 wherein the magnetized element comprises a permanent magnet.

25. Apparatus as defined in claim 21 wherein the biasing means comprises a spring.

26. Apparatus as defined in claim 21 wherein at least one of the elements of the magnet couple is a roller.

27. Apparatus as defined in claim 21 wherein the magnetized element and the armature element are rollers.

28. Apparatus as defined in claim 21 wherein the movable element of the magnet couple is a roller.

GEORGE F. WATSON.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 1,077,818 Eagar Nov. 4, 1913 1,218,988 Droitcour Mar. 13, 1917 1,701.861 Niblack Feb. 12, 1929 2,129,230 ONeil Sept. 6, 1938 2,260,771 Buccicone et al. Oct. 28, 1941 2,318,132 Welk May 4, 1943 

